Rapid advance in the manufacture technology of the TFT (thin-film transistor) enhances the function capacity of the flat display panels, such as an LCD (liquid crystal display) panel and organic light emitting diodes. The LCDs are greatly employed in the PDA (personal digital assistant), notebook computers, digital cameras, and video-and-audio recording instruments and mobile phones. The manufacturers worldwide have devoted themselves to further research and thus improve the materials, processes and equipments. The qualities of the LCD are accordingly and largely promoted while the cost goes down day-by-day.
FIGS. 1A and 1B respectively show top planar and sectional views of a pixel unit in the conventional LCD panel, and includes upper and lower glass substrates 2, 1 and a liquid crystal layer sandwiched between the upper and lower glass substrates 2, 1. As shown in FIG. 2A, during the construction, a first conductive layer is fabricated on the lower glass substrate 1 by photolithography to define a pattern which is later etched to form a horizontally extending scan line 11. A dielectric layer 13 and a second conductive layer are successively fabricated on the scan line 11 by deposition. Etching operation is later conducted on the second conductive layer to form a data line 12, a source and a drain in such a manner that the data line 12 transversely crosses the scan line 11. Under this condition, overlapped sections of the data line 12, the dielectric layer 13 and the scan line 11 cooperatively form a projection 15 that protrudes upwardly from the lower glass substrate 1 while overlapped sections of the source, the drain, the dielectric layer 13, and the scan line 11 cooperatively form a TFT adjacent to the projection 15. On the other hand, a color filter, a common electrode layer can be fabricated on the upper glass substrate 2. The upper glass substrate 2 is mounted on the lower glass substrate 1 in such a manner to define an enclosed space therebetween. A liquid crystal solution is injected into the enclosed space so as to form a liquid crystal layer between the upper and lower glass substrates 2, 1.
Note that in the past, prior to injecting the liquid crystal solution and in order to provide rigidity of the conventional LCD panel, a plurality of plastic beads are sprayed onto one of the glass substrates before the other glass substrate is assembled there over. The distribution of the plastic beads within the liquid crystal layer cannot be precisely controlled and is therefore uneven. In addition, the plastic beads are subjected to move within the liquid crystal layer, thereby causing uneven brightness through out the entire length of the display screen.
In FIG. 1B, the spacer unit 21 is usually formed on the upper glass substrate 2 by photolithography in order to overcome the aforesaid uneven distribution and displacement problems, wherein the spacer unit 21 abuts against the lower glass substrate 1. Note that in order not to interfere with the light transmission through the LCD panel, the spacer unit 21 is generally confined within the opaque domain formed on the upper glass substrate 2 in alignment with the scan line 11 and between two adjacent data lines 12 such that the spacer unit 21 will not cover the pixel electrode of the lower glass substrate 1. Since no adhesive is applied between the spacer unit 21 and the lower glass substrate 1, left-and-right sidewise movement between the upper and lower glass substrates 2, 1 is still possible when an external force is applied onto one of the substrates 2, 1. A relatively large displacement between the upper and lower glass substrates 2, 1 may result in exposure of the opaque domain in the upper glass substrate 2, which, in turn, results in light leakage problem and uneven distribution of brightness through out the of the conventional LCD panel.